Pipe forming method and apparatus

摘要

In a pipe forming process using bending rolls, load applied to an upper roll (34) is reduced to suppress the deflection of the upper roll, thereby suppressing the creation of a large end gap at the longitudinal center of the pipe, thus enabling the production of high-strength, thick-walled, elongated pipes. This is achieved by effecting pipe forming work on sheet material (10) such that the spacing L of the lower rolls (32) satisfies the condition (Dp + Dwl) > L≥0.85 (Dp + Dwl), where Dp represents the outside diameter of the product pipe and Dwl represents the diameter of one of the plural rolls. An apparatus for carrying out the method is also disclosed.